1. Field of the Invention
The body's maintenance of normal thyroxine is an important factor in good health. Since many ailments can be attributed to an enhanced or diminished concentration (hyperthyroid or hypothyroid), the determination of thyroxine in blood samples has become a common occurrence. There are a number of different techniques which can be employed for the determination of thyroxine. The more accurate assays depend upon specific protein recognition for thyroxine. By providing a competition between a tagged thyroxine and the thyroxine for a specific binding protein, the amount of the tagged material which becomes bound to the protein or remains free can be correlated with the amount of thyroxine in the serum.
Thyroxine is a highly functionalized compound and is also very hydrophobic. Thyroxine is therefore capable of binding both specifically and non-specifically to a wide variety of proteins. In addition, its ability to bind specifically to proteins can be affected by a number of different materials, e.g. surfactants.
The existence of various naturally occurring materials which interfere with the accuracy of results obtained in thyroxine assays is a serious problem. First, standards are normally run with known amounts of thyroxine which may not have the interferants. The results obtained with the serum samples will therefore differ from the standards. In addition, correlations between different techniques for thyroxine determination cannot be made, since the various interferants may interfere differently with the different techniques. Finally, since individuals will vary as to the amount of the interferants present in their serum, even from day to day, no reliable comparison can be made of the results. It is therefore essential that a thyroxine assay take account of the presence of the interferants and either remove the interferants, deactivate their effect, or be able quantitatively to account for their presence.